This invention relates generally to fluid or hydraulically operated actuators wherein a piston translates within a cylinder and, more particularly, to a fluid actuator having internal locking means for locking the piston relative to the cylinder to provide an actuator of desired length, and to unlock the piston when desired.
Fluid actuators, operated by hydraulic or pneumatic pressure, are utilized in a large variety of applications, such as in extensible/retractable supports for aircraft landing gear, doors, etc. One of the most important features in such actuators is the incorporation of a locking mechanism which can rigidly maintain the actuator in a fully extended or fully retracted position after the hydraulic pressure, which causes the extension or retraction, has ceased.
Several designs are known for providing a locking capability in fluid actuator cylinders. One of the most common locking mechanisms involves a finger and ball arrangement such as shown in U.S. Pat. No. 3,429,233. Although these designs have proved adequate in certain applications, they suffer several drawbacks. For example, such devices are not capable of handling high loads with secure locking power and often require frequent replacement of parts, particularly ball bearings, when locking and unlocking are carried out under heavy loading conditions. The same disadvantages hold true for finger lock devices such as disclosed in U.S. Pat. No. 3,498,182.
A significant drawback to all known actuator locking mechanisms, particularly in aircraft and like applications, is that they are generally massive and large in size. The envelope required to house such locking mechanisms must necessarily be large and cannot be significantly reduced in size. This has presented a significant obstacle to the full utilization of the higher pressure, smaller size hydraulic system components which have recently been developed to allow substantial reductions in the weight of the overall hydraulic system.
Thus, while conventional hydraulic systems operate at about 3,000 p.s.i., recent efforts have resulted in increased operating pressures of up to 8,000 p.s.i., thereby permitting a reduction in the size of the system components in a ratio of about 8 to 3. However, because conventional locking mechanisms cannot be reduced in the same proportion, or even reduced at all, they represent a significant limitation on the ability to take full advantage of light weight, high pressure hydraulic components.
Ideally, the locking devices in such actuators should be formed in such manner that they do not overly increase the size of the actuators and that they can withstand repeated applications of relatively high loads, as compared with the forces exerted by the hydraulic pressure.
Accordingly, it is an object of the present invention to provide a new and improved fluid actuator, including locking means therefor. It is also an object of the invention to provide a new and improved actuator and locking means capable of functioning under high load conditions. Another object of the invention is to provide a new and improved actuator and locking means which enable secure locking of parts over relatively long term use under high load conditions, with relatively infrequent replacement of parts required.
It is still another object of the invention to provide a new and improved actuator and locking means which utilizes the convenience of ball bearings but does not subject the ball bearings to the locking forces. Further, it is an object of the invention to provide a new and improved actuator locking means which permits the size of the actuator envelope to be reduced in essentially the same proportion as the other components of the hydraulic system when higher pressure, lighter weight components are utilized.
It will be appreciated by those skilled in the art that although certain objects and advantages of the invention are set forth herein, other advantages will be appreciated herefrom or may be realized from practice with the invention which may be attained by means of the instrumentalities and combinations disclosed herein and defined in the appended claims. Accordingly, the invention resides in the novel parts, constructions, arrangements, instrumentalities and combinations herein shown and described.